Google has been declared "a monopolist" in a landmark decision that may shake things up in Silicon Valley. The decision came down Monday in US District Court for the District of Columbia.

This blockbuster case has been ongoing for several years, with the trial having begun last September. The US Department of Justice argued that Google had become an illegal monopoly, and in a 277-page ruling, Judge Amit P. Mehta agreed.

As the New York Times reports, Mehta ruled that Google had cultivated and maintained a monopoly over internet search in part by paying companies like Samsung and Apple to make its search engine the default in their mobile browsers.

"Google is a monopolist, and it has acted as one to maintain its monopoly," Mehta wrote.

This is the first antitrust case against a big tech company since the government's case against Microsoft over two decades ago, and it could lead to Google/Alphabet needing to make major changes to how it does business.

The ruling further finds that Google has an illegal monopoly over the text-based ads that appear in its search results. Mehta found that Google was able to inflate the prices of search ads because of this monopoly.

Per the Times, Mehta will now recommend a remedy for the company, with the possibility of having to break apart its search or advertising businesses.

In a statement, Jonathan Kanter, who leads the Justice Department's antitrust division, said, "This landmark decision holds Google accountable. It paves the path for innovation for generations to come and protects access to information for all Americans.”

Google responded to the ruling, with the company's VP of global affairs, Kent Walker, trying to give it a positive spin.

"This decision recognizes that Google offers the best search engine, but concludes that we shouldn’t be allowed to make it easily available. As this process continues, we will remain focused on making products that people find helpful and easy to use," Walker said.

The ruling is a major win for competitors like Microsoft, whose Bing search engine has for over a decade tried to carve out a share of the search space, with little traction.

Previously: Feds’ Blockbuster Antitrust Suit Against Google Is Underway, Could (Maybe) Break Up Google As We Know It

Photo: Pawel Czerwinski